The present invention relates to a method and an apparatus for cleaning a flame detector applicable to a gas turbine activating combustor.
Among typical ignition systems of gas turbines, there is a spark-ignition system in which high-voltage current is used to fly sparks in a gap of a spark plug, thereby firing atomized fuel. FIG. 2 shows a system diagram of the ignition system.
Referring to FIG. 1, there is shown a four-port solenoid valve 11, which is energized by means of a valve driver 11a in response to a command for firing, whereupon control air 10 is fed from a forcing air system 12 into an air cylinder 13. As this is done, a spark plug 14 is inserted into an inner cylinder of a combustor (not shown). At the same time, atomized fuel is ejected from a spray jet of a fuel nozzle, while fuel atomizing air is blown out from around the fuel nozzle.
When ignition is completed, ignition transformer operation is canceled, and the solenoid valve 11 is de-energized, so that the control air 10 is fed into a drawing air system 15, and the air cylinder 13 is returned to its original position. Thereupon, the spark plug 14 is drawn out of the inner cylinder of the combustor.
The spark plug 14 is inserted into and drawn out from the inner cylinder of the combustor in order to prevent the plug 14 from burning in a high-temperature combustion gas. The pressure of the control air 10 for controlling the spark plug 14 ranges from about 4 to 10 kgf/cm.sup.2.
Referring now to FIG. 2, a conventional flame detector 16 for detecting firing by means of the ignition system will be described. The detector 16 is attached to each side of the spark plug 14 of the combustor. As shown in FIG. 2, a light sensor glass 17 is provided on the combustor side of the flame detector 16, whereby the intensity of received light is detected.
In the case where the conventional flame detector is used in a PFBC (pressurized-fluid-bed combined power plant) or IGCC in which coal fuel is used for single-fuel firing, dust, soot, etc. are deposited on the light sensor glasses of the flame detector during operation, sometimes inhibiting flame detection in the next cycle.
Thus, the conventional flame detector requires dismantling for glass cleaning once a week or every several weeks.